Final answer:
The father of a child with AB blood could have AB, A, or AO (phenotypically A) blood types. The B allele from the mother and the A allele from the father result in the child's AB blood type. The woman with type B blood can donate to a husband with type B or AB blood.
Step-by-step explanation:
When a woman has type B blood and her child has type AB blood, the possible blood types of the father can be deduced using the principles of ABO blood type inheritance. The mother's type B blood indicates that she has either the BB or the BO genotype. Since the child has type AB blood, the child must have received one A allele from the father and one B allele from the mother. Therefore, the father can have blood type AB, A, or possibly AO (which phenotypically is blood type A). This is because the presence of the A allele is necessary for the child to have type AB blood. It's not possible for the father to have type O blood (OO) since this would not provide the necessary A allele.
Considering this, when it comes to donating blood, a woman with type B blood can only donate to her husband if he has blood type B or AB. Since type AB individuals are considered universal recipients for blood transfusions, they can receive blood from any type without concerns of ABO blood type incompatibility.